combobox with javascript

i have a combobox which have about 50 items in it,i want to show that on selecting diff items ,it maps those values on label or textbox.i want to use javascript for this,if else condition of javascript ,

var x=document.getelementbyid("cmb1");
if(x="apple")
{
show image of apple on update panel;
}
 like this.all coding to be done with javascript;


help needed,
amitesh